In the fusion bonding of tubular members to one another it is known to employ external clamping devices which define a circumferential area into which an inert gas may be introduced around the abutting ends of the tubes. For an example of such a prior art clamping device, reference may be had in published German Patent Application Ser. No. 1,959,323. In the case of austenitic steel, however, it is necessary to provide the protective gas atmosphere both outside the tube and also at the inside of the weld bead when tungsten-inert-gas (TIG) welding is employed. Accordingly, when the present external clamping devices are employed, the entire internal volume of the tubes to be welded will be filled with inert gas or special chambers filled with inert gas will be employed. These are both time-consuming procedures and wasteful of the relatively expensive gas.
A further deficiency of prior tube welding devices and procedures is the inability to establish and maintain alignment of the edges of the tube sections which are to be joined. Such misalignment may occur because of tolerances in the production of the tubes, both in diameter and in roundness, and also because of shrinkage of the tubes which occurs during the fusion bonding operation.